gy 
Tiar procefs, which the Indians keep a profound fecret.’ To fuit the 
different purpofes for which it is employed in South America, the ~ 
Caoutchouc is fhaped into various forms;* but it is commonly brought 
to Europe in that of pear-fhaped bottles, which are faid to be formed 
by {preading the juice of the Siphonia over a proper mould of clay, and 
as foon as one layer is dry another is added till the bottle be of the thick- 
nefs defired. It is then expofed to a denfe fmoke, or to a fire, until 
it becomes fo dry as not to ftick to the fingers, when by means of 
certain inftruments of iron or wood it is ornamented on the outfide 
with various figures. This being done it remains only to. pick 
out the mould, which is eafily effe€ted, on being firft foftened with 
water. 
The fubftance, thus manufactured, is fo well known as to render 
any particular defcription of it unneceflary. It may be fubje@ed to 
the ation of fome of the moft powerful menftrua without fuffering 
the leaft change, while its pliability and elafticity are eminently 
peculiar to itfelf. It is true that the lactefcent juice of feveral vege- 
tables may be converted into a fubftance refembling the Caoutchouc, 
but no art has yet been difcovered to give it the fame properties. 
The Chinefe elaftic refin is faid to be prepared of caftor oil and 
lime;'‘ or, according to Retzius, it is nothing but a certain exprefled — 
oil evaporated by heat :* hence its eafy folubility. 
‘With a view to inveftigate the interefting nature of the Caoutchouc, 
and to render it of more general utility, feveral able chemifts have 
been diligently employed, efpecially Macquer,” Achard,' Juliaans,* and 
Berniard,' from whom its chemical hiftory is to be learned: our duty 
however is to ftate only fome of the principal facts. | 
Se 4 Vide Rozier obf et. mem. fur la phyfique. tom. 1. p. 464. ; 
© The curious diverfity of figures in which this fubftance was fold in Portugal is 
noticed by Mr. Twifs. See Travels through Portugal and Spain. 323. 
fy. Faujas de Saint-F ond Suite de la defeription des experiences aéroflatiques tom. 2. 
— . ' ; a Pharm. reg. veg. p. 60. 
: * Mem. de LV’ Acad. des Sc. de Paris, pour 1768. 
5 Chymifch phyf. Schriften cap. De refina elaflica. * Diff. de Refina elaflica Cayennenfi. 
; 1 See Rozier Ob. fur la Phyfique. tom. 17. 
No. 19.—Part II. 2F Though 
